tag:blogger.com,1999:blog-9959776.post2381444796726393142..comments2024-02-15T04:42:41.606+00:00Comments on James' Empty Blog: Wiley Interdisciplinary Reviews: Climate ChangeJames Annanhttp://www.blogger.com/profile/04318741813895533700noreply@blogger.comBlogger14125tag:blogger.com,1999:blog-9959776.post-88222049448309427362010-08-11T17:12:55.213+01:002010-08-11T17:12:55.213+01:00Tom, he would also need 30 or so years of prior fo...Tom, he would also need 30 or so years of prior forcings, solar ghg, etc. to wven start. The model had to be validated against past observations. In 1950, Mauna Loa was not even a model, and the method had not yet been invented.<br /><br />This is not to be snarky, but to point out that there is an entire edifice that Hansen had to stand on (see the banner for JeB).EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-32487686039503084222010-08-11T14:55:23.230+01:002010-08-11T14:55:23.230+01:00OK, I will read the paper. However if you could i...OK, I will read the paper. However if you could indulge me for one last question: what if Hansen had the models and methods of 1988 available to him in 1950? What would his prediction have looked like and what would Jules' analysis have concluded 30 years on?Tom Chttps://www.blogger.com/profile/03793192912187740419noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-12407388812822855572010-08-10T20:57:34.500+01:002010-08-10T20:57:34.500+01:00Tom,
Based on your comment, I can only surmise th...Tom,<br /><br />Based on your comment, I can only surmise that you don't know what "skillful" means in this context. It is a standard term of art which is defined in the paper, you could try reading it.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-23333884363668572132010-08-10T20:11:26.230+01:002010-08-10T20:11:26.230+01:00As Hansen himself said, any half rational GCM has ...As Hansen himself said, any half rational GCM has to get global temperature anomaly ~right for 20 years. The constraints on the sensitivity and the forcings (absent the sun going out or fossil fuel burning stopping) are not strong enough to move the prediction much.<br /><br />Global temperature is much too easy to be a real test over less than a century.EliRabetthttps://www.blogger.com/profile/07957002964638398767noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-9549846455423060862010-08-10T16:58:05.642+01:002010-08-10T16:58:05.642+01:00James -
I don't think you realize the problem...James -<br /><br />I don't think you realize the problem that the 1950-1980 period represents. What combination of inputs led to the flat GTA during this period? If there is no good answer to this the models can't be skillful. Saying that the curve goes up from the late 1900s on and models predict a continued increase is pretty lame.Tom Chttps://www.blogger.com/profile/03793192912187740419noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-30363657829547923972010-08-09T22:07:48.064+01:002010-08-09T22:07:48.064+01:00Well, the focus was on a 20y forecast, since that ...Well, the focus was on a 20y forecast, since that is the amount of data we now have for validation, but yes, we tried a range of different hindcast periods for fitting the trend and for averaging for the sake of persistence - up to 30y, IIRC. For a very long hindcast interval, you can't fit many instances into the data (and they all overlap, so are not independent).James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-49118461862073787612010-08-09T19:58:58.092+01:002010-08-09T19:58:58.092+01:00"Trying to fit a trend does worse than just a..."Trying to fit a trend does worse than just assuming no change. "<br /><br />How do you do this? Do you go through the record testing the various predictions Eg, did you test whether the next 22 years of the record was better predicted by the trend of the previous N years, for N between 1 and 80? (80 is chosen because we have about 100 years of temperature record, and we have to at least test a prediction on 1966-1988 in order to test a model which will be used to predict 1988 to 2010). <br /><br />I believe you that predicting "no trend" might beat any trend prediction regardless of N, but I'd still be interested in knowing whether you did the full calculation...<br /><br />-MAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-9959776.post-62918999797053697242010-08-08T07:19:02.896+01:002010-08-08T07:19:02.896+01:00There certainly are things to complain about, incl...There certainly are things to complain about, including the two I mentioned, but I have no worries about the article getting any serious attention. I mentioned it because I think it is grounds for worrying about the future direction of the journal. But for now, I'm not arguing that there's a reason to not submit papers to it.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-59677749954451249772010-08-07T02:21:01.249+01:002010-08-07T02:21:01.249+01:00Steve, that is clearly labelled as an opinion piec...Steve, that is clearly labelled as an opinion piece, and I don't see much to complain about there. (I may be missing something though - I'm not really a hockey player.)James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-80695242841705700542010-08-07T02:15:31.861+01:002010-08-07T02:15:31.861+01:00Tom, we checked which of the two obvious baseline ...Tom, we checked which of the two obvious baseline forecasts would have performed best on average over the whole historical record. Trying to fit a trend does worse than just assuming no change. Previous apparent trends (eg 1880-1910, 1910-1940) had all abruptly ended, there was no reason to assume things would be different in 1988 - unless you accept the model's prediction, of course...which is precisely the point.<br /> <br />I see now there is a typo in the graph - 1990 should be 1900 of course.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-74467974682990163172010-08-06T22:16:25.442+01:002010-08-06T22:16:25.442+01:00And as it turns out we saw very quickly indeed. H...And as it turns out we <a href="http://www3.interscience.wiley.com/cgi-bin/fulltext/123397276/PDFSTART?CRETRY=1&SRETRY=0" rel="nofollow">saw</a> very quickly indeed. How bold of Esper and Frank to approve of Esper & Frank 2009's assessment of work on the MWP so definitively.<br /><br />I do think Zorita's background makes him perfectly suited to be one of the new Proxy Cops.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-39778797527220874342010-08-06T22:06:53.144+01:002010-08-06T22:06:53.144+01:00James -
This is not persuasive. Why was the null...James -<br /><br />This is not persuasive. Why was the null hypothesis closer to measurements from 1950 to 1980?Tom Chttps://www.blogger.com/profile/03793192912187740419noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-52987708822723156112010-08-06T20:59:29.520+01:002010-08-06T20:59:29.520+01:00Hey, it's free for now, so don't complain....Hey, it's free for now, so don't complain. And we are hardly the sort of people to turn down invitations to present our opinions (well, as I said, I almost did). Actually, there is not a good open access option for most of my work, as I have grumbled before, what with the EGU climate journal focussing specifically on paleoclimate.James Annanhttps://www.blogger.com/profile/04318741813895533700noreply@blogger.comtag:blogger.com,1999:blog-9959776.post-6554714210182163372010-08-06T19:37:39.587+01:002010-08-06T19:37:39.587+01:00Hmm, yet another pay-to-view journal. Weren't...Hmm, yet another pay-to-view journal. Weren't there open-access ones you could have gone to instead?<br /><br />Anyway, the combination of Hulme, von S. and RP Jr. causes me to think the obvious Dark Thoughts. We shall see.Steve Bloomhttps://www.blogger.com/profile/12943109973917998380noreply@blogger.com